Take off how many bunk supports fit along a hull support length at a chosen spacing (supports ≈ floor(L / spacing) + 1), and show the average gap.
This tool helps when you want a trailer bunk spacing / support count estimate with the assumptions written down. Enter hull support length (in), desired spacing (in), and number of bunks (rows).
Take off how many bunk supports fit along a hull support length at a chosen spacing (supports ≈ floor(L / spacing) + 1), and show the average gap.
Along one bunk, support count is floor(support_length / spacing) + 1 so both ends are covered. Actual average spacing is support_length / (count − 1). Multiply by bunk rows for a total takeoff.
supports_per_bunk = floor(L / spacing) + 1
avg_spacing = L / (supports_per_bunk − 1)
total_supports = supports_per_bunk × bunk_rows
Not a structural engineering stamp.
Example inputs from the form defaults — Hull support length (in) = 144; Desired spacing (in) = 24; Number of bunks (rows) = 2 — are chosen to be plausible coastal/cruising figures, not your boat’s survey.
Compute with: supports_per_bunk = floor(L / spacing) + 1 avg_spacing = L / (supports_per_bunk − 1) total_supports = supports_per_bunk × bunk_rows.
When the calculator and your scratch math disagree, fix units first; the trailer bunk spacing / support count model is only as good as consistent inputs.
This trailer bunk spacing / support count page models the arithmetic shown in the formula box only.
Bunk length is the board; this page spaces the vertical supports under the contact length.
Follow trailer maker guidance and hull shape. Closer spacing near the bilge can help — this tool only does the arithmetic.
floor(L/spacing)+1 may leave a shorter end bay; avg_spacing shows the even split if you redistribute.